Dendrimers and hyperbranched polymers represent a novel class of structurally controlled macromolecules derived from a branches-upon-branches structural motif (Tomalia et al., Angew. Chem. Intl. Edit. 29:138-175 [1990]; and Naylor et al., J. Am. Chem. Soc. 111:2339-2341 [1989]). Dendrimers are well defined, highly-branched macromolecules that radiate from a simple organic molecule as a core and are synthesized through a stepwise, repetitive reaction sequence that guarantees complete shells for each generation leading theoretically to products that are unimolecular and monodisperse (Tomalia et al., Macromolecule 24:1435-1438 [1999]; and Dvornic and Tomalia, “Dendritic polymers divergent synthesis: starburst poly(amidoamine) dendrimers,” in Salamone (ed.) The Polymeric Materials Encyclopedia: Synthesis, Properties and Applications,” (CRC Press: Boca Raton) [1996]). The synthetic procedures developed for dendrimer preparation permit nearly complete control over the critical molecular design parameters, such as size, shape and shell/core chemistry. Synthetic techniques that have proven effective for dendrimer production include the divergent strategy of Tomalia and co-workers (Tomalia et al., Angew. Chem. Intl. Edit. 29:138-175 [1990]; and Naylor et al., J. Am. Chem. Soc. 111:2339-2341 [1989]), the convergent growth strategy of Fréchet and co-workers (Hawker et al., J. Chem. Soc. Perkins Trans. 12:1287-1297 [1993]; Fréchet, Science 263:1710-1715 [1994]; and Fréchet, Science 269:1080-1083 [1995]), and the self-assembly strategy of Zimmerman and co-workers (Zimmerman et al., Science 271:1095-1098 [1996]). These methods have made possible the generation of synthetic macromolecules with unique combinations of properties (Bell, Science 271:1077-1078; van Hest et al., Science 268:1592-1595 [1995]; Jansen et al., J. Am. Chem. Soc. 117:4417-4418 [1995]; and Jansen et al., Science 266:1226-1229 [1995]).